The field of this invention is liquid-level indicating devices.
In situations in which a liquid is to be stored in a container or tank and withdrawn for use as required, it is desirable that the amount of liquid remaining in the tank at any time be easily ascertainable. Typically, a float-actuated mechanism is inserted into the tank to drive an external indicating means. The float rises and falls with the liquid level in the tank and is calibrated in conjunction with the indicating means to register the amount of liquid in the particular container. Representative devices of this type are described in U.S. Pat. No. 2,716,341 to W. T. Ilfrey et al. and U.S. Pat. No. 2,722,835 to D. Ragland.
A gauge of this general type is often used in private homes and like premises to indicate the amount of fuel oil remaining in an oil storage tank. Such tanks are usually located in the basement of the building where the heating or hot water system, which is powered by the oil, is generally found and where the occupant can conveniently periodically check the amount of oil remaining therein. Oil is typically added to the tank from an inlet point located outside of the premises and connected to the tank by a conduit.
With the recent rapid rise in the price of such fuel oil, homeowners have become increasingly sensitive to the cost of maintaining a sufficient supply of oil in their tanks. Furthermore, the high price of the fuel has encouraged some disreputable dealers to overcharge consumers when filling their storage tanks, claiming to have added more oil thereto than they actually have. To avoid such abuses, many homeowners have begun to carefully watch the gauges on their tank. By reading the gauge just before and immediately after a delivery, the precise amount of oil added to the tank can be determined and then compared with the dealer's charges. However, often the homeowner may not know when oil is to be delivered. He may not be at home when the dealer arrives, or he may be on an extended vacation at the time and in such cases it is virtually impossible to be sure that an accurate, independent determination of the amount of oil delivered can be made.
The prior art teaches a number of similar devices for indicating the amount of liquid, such as oil, that has been added to a container. U.S. Pat. No. 1,453,716 to C. F. MacGill describes a fluid registering mechanism for such purpose specifically adapted for use with an automobile gasoline tank. Use of the MacGill device would appear to be limited to tanks of limited capacity due to the gearing arrangement by which the cumulating counter is driven. Furthermore, there is no suggestion in the disclosure as to how the interlock mechanism on the device for disabling the counter at all times other than when the tank is being filled might be adapted for use with a liquid storage container to which liquid is added from a remote location.
U.S. Pat. No. 1,679,285 to H. F. Wright teaches a gauge and recorder for indicating both the amount of liquid added to a container and the amount withdrawn therefrom. This device records such information on a paper chart and requires the user to replace the chart on a daily basis, necessitating constant supervision. The Wright apparatus is therefore highly inconvenient for home use where a daily determination of the liquid level in the storage tank and the amount of liquid added thereto is neither necessary nor desired.
There is, therefore, a need for a direct reading indicating device that combines a gauge showing the quantity of liquid remaining in the tank with a second gauge which records the amount of liquid that has been added to the tank irrespective of liquid since withdrawn therefrom, which is practical and convenient for unattended use by an average homeowner and is adapted for mounting atop a home storage tank.